1. Field of the invention
The present invention relates to a vacuum apparatus for the treatment of workpieces and having at least one treating chamber for said workpieces and a central evacuable distribution chamber and including a first transporting mechanism and locks through which the workpieces can be placed by the first transporting mechanism into the distribution chamber and retrieved by same after having been treated.
2. Description of the prior art
In the periodical Solid State Technology of October 1987 (pages 55/56) such a multi-chamber apparatus for the treating of silicon wafers is known which includes a robot arm located in a central distributing chamber and which places the individual semi-conductor disks in accordance with a set programme into the individual treatment chambers and retrieves these disks out of such chambers after having received a certain treatment such as a coating. A plurality of treatment chambers may be connected to one such central distribution chamber whereby the semi-conductor disks can be transported through the distribution chamber from one treatment chamber into another treatment chamber such that they must not be transported in the free environment between the individual treatments. In case of extremely delicate treatments there is, however, a danger that residual gases which e.g. are necessary for a treatment step in one treatment chamber could reach another treatment chamber where they disturb the treatment being made there or it is possible, that particles which possibly were raised during the one or the other treatment step are dragged along. It is also possible that particles which together with not yet treated semi-conductor wafers are brought from the outer chamber into the distribution chamber and then settle onto already treated semiconductor disks when moving across and detrimentally influence the following treatments to be made with these not as yet treated semi-conductor disks.
It already has been proposed to decoupage the individual treatment steps by pressure step locks which are out in the circuit ahead of the treatment chambers e.g. by means of a so called pressure step system which consists of three vacuum chambers which can be evacuated separately and where the wafers are transported through corresponding slots in the walls between the individual chambers into the treatment chambers. The main object of the pressure step locks was thereby only to maintain a differential pressure between the individual chambers of the vacuum system.